ANOTHER NO SPARK 74 charger

[Ernie ingling]

So what happened??

 

[WheelsOfTerror]

Interlock system ( similar to the NSS on transmission but with ground ) won't allow to crank the engine. Just affects the cranking circuit from the ign switch. If you don't have spark is for any other reason way ahead from the interlock system. It can be bypassed on any wished form... jump out the yellow wires at the reset/override button, turn around yellow wires at bulkhead, crank it out straight at starter relay with a jumper wire or even a wrench, but if doesn't get spark if engine is turning, the interlock has nothing to do.

At coil you should have between 4.5-9 volts ( depending on engine bay temp and RMPs once fired up ) with key in RUN and 11-12 volts while cranking

ECU should get around same voltage on blue wire with yellow trace but stages reversed.

This both readings are due the ballast. If your are not, it can be either ballast, ign switch or bad/broken contacts somewhere ( bulkhead, plug down the column, wires broken )

One way to know ballast is in working order is the brake warning signal on cluster ( oil too if standard cluster ). Key in RUN will obviously light on these lights. While cranking these lights will dimm out. If lights off, something of the ign1/2 switching system previously explained is not working propperly

ECU must be good grounded. You can check the ground with continuity between one of its pins and body ground... is one of the dist pick up coil wires, can't recall right now which one. Will post later. ( if pickup wire has been replaced for a newer unit with black and orange wires, is the one what feeds the red wire )

Pick up coil continuity can be checked too. It should be between 150 and 900 ohms ( tipically 250-290 rate ) and isolated from body ground. You can check it at dist pickup coil plug &/or ECU plug. That will assure the plugs to pickup coil are good too. It happened to me that quite often I had to shake the dist plug wire to be able to fire up the engine... bad contact into the dist plug OR broken wires inside still with pickup coil good. Sometimes we replace the pickup coil when is just the plug what got damaged, and you can replace/fix just that keeping the pickup coil inside the dist in place.

Black wire with yellow trace at ECU must read continuity from end to end of course ( - lead of coil ). Green wire with red traces too between ECU plug and ballast. Important if is a 5 pins ECU, not so important if 4 pins since this wire gets to nowhere with 4 pins ECU.

If everything of this tested good the next reasons could be, damaged distributor rotor or cap... or ECU itself

My '74's problem is that it would start with the keyed ignition and then stop immediately once you put the key into run position. We were able to get it running and idling to tune the rebuilt carb by putting power directly to the coil and it idled fine for that.

to tackle the keyed ignition problem I started by changing the ignition switch (I had ordered a spare in case this issue came up) afterward it doesn't start from the key at all but you can initiate the starter from the starter relay, although the engine will not turn over.

Tomorrow I will check and see where the 12v stops in the big yellow wire coming from the ignition switch- I suspect the wires are not connecting at the harness under the steering wheel or at the bulkhead, since it can be cranked from the starter relay ok (though it does not turn over now that I changed the ignition switch in the column).

What wire/wires do I need to worry about that would cause it to shut off in "run" position on the ignition switch? I see on the wiring diagram that brown and black are labeled "Ignition 1"' and "Ignition 2"? Could be yellow, brown or black possibly?

 

[WheelsOfTerror]

So what happened??

If you're asking about my Charger- I bypassed the seatbelt interlock but am still chasing down the errant wires so that I can start and idle the car from the drivers seat using the keyed ignition switch. The wires are original mostly so I'm trying to make sense of the rat's nest, hoping to get the car driveable without ordering an entirely new harness- a lot of it is fine.

If it isn't too damn hot out there tomorrow I will get under the dash with my voltmeter and see what's what. If it is hot as hell (June in Los Angeles can be) I'll wait till the late afternoon or do it in the dark when it's nice and cool.

Wish me luck and I'll keep y'all posted

 

[Nacho-RT74]

My '74's problem is that it would start with the keyed ignition and then stop immediately once you put the key into run position. We were able to get it running and idling to tune the rebuilt carb by putting power directly to the coil and it idled fine for that.

Did you check if the brake light on cluster goes off while cranking?

to tackle the keyed ignition problem I started by changing the ignition switch (I had ordered a spare in case this issue came up) afterward it doesn't start from the key at all but you can initiate the starter from the starter relay, although the engine will not turn over.

Remove the thin gauge black wire from the new switch ( it it got it ). Replacement switches use to have this provision for some later cars which needs to require it for some weird ground signal while cranking as far I recall, AND on our cars it matches with an orange wire for column shifter light. If you try to crank up some day the engine with lights on, will blow the cluster light fuse.

Tomorrow I will check and see where the 12v stops in the big yellow wire coming from the ignition switch- I suspect the wires are not connecting at the harness under the steering wheel or at the bulkhead, since it can be cranked from the starter relay ok (though it does not turn over now that I changed the ignition switch in the column).

What wire/wires do I need to worry about that would cause it to shut off in "run" position on the ignition switch? I see on the wiring diagram that brown and black are labeled "Ignition 1"' and "Ignition 2"? Could be yellow, brown or black possibly?

Yellow is just to trigger the starter relay and nothing else

Brown bypasses the ballast while cranking ( ign2 )
Blue is the circuit you are getting trouble ( ign1 ) which it uses to take very well to the ballast failure BUT:

The start up while cranking but stalling returning the key it can be anything from ballast, to bulkhead or ign switch. HOWEVER on this ocassion is not the ballast, because if you feed the coil from batt and engine keeps alive after crank it, the ECU is getting sourced from the same coil jumper wire THROUGHT the ballast ( assuming something of the rest is failing )

Go straight for the 12 volts check with key in RUN at ballast, or anywhere into the blue wire circuit... regulator, alt field, choke control feed or even the interlock reset button plug. This would take to the bulkhead connection at engine harness.

This failure will take to get off the brake light on cluster while cranking.

On normal conditions an underdash harness never needs really a full replacement unless previous owners got it highly "highjacked". The tipical failures on them is the Charging circuit network which when fails to the max, it takes to death the wires around them up to ammeter what due overheats caused by a heavy short it melts all around. The first diagnosis for them is a melted bulkhead conection caused by the low rate amps installed on our cars from factory giving over stressed the charging circuit, along with the low capacity of the packard terminals to hold the high stress on them, but if wire is still good, a deep mantenience on terminals and a bulkhead replacement is quite enough. Some of the fails with the bulkhead is not more than dirt and grease on terminals.

However it's weird you can't start up the engine with the new switch. You should get AT LEAST the same problem than with the original switch ( which I would try to keep on car )

 

[Nacho-RT74]

This is the replacement switch I meant. If you got one with this wire circled on plug, remove it. Some good brand replacements it use to get instructions sheets with them but most they don't

 

[WheelsOfTerror]

View attachment 962231 This is the replacement switch I meant. If you got one with this wire circled on plug, remove it. Some good brand replacements it use to get instructions sheets with them but most they don't

View attachment 962231 This is the replacement switch I meant. If you got one with this wire circled on plug, remove it. Some good brand replacements it use to get instructions sheets with them but most they don't

I will take a look at my replacement switch tomorrow morning and see what wire is in that position on the harness. If it is the same as in your picture, why am I removing this wire?

Also, just to be thorough- there is an orange wire going to the gear indicator light on top of the steering column- my new ignition switch had a black wire going into the same terminal the orange wire was going into on the original switch. I pulled that black wire and put the orange one where it was to make sure it was wired the same way I found it originally. Was this a mistake?

 

[WheelsOfTerror]

Did you check if the brake light on cluster goes off while cranking?

I did not but now that I know it's important I will look



Remove the thin gauge black wire from the new switch ( it it got it ). Replacement switches use to have this provision for some later cars which needs to require it for some weird ground signal while cranking as far I recall, AND on our cars it matches with an orange wire for column shifter light. If you try to crank up some day the engine with lights on, will blow the cluster light fuse.

I didn't see this on my original reply- I did this and now that I read I realize I did the right thing. Glad to know the weird reason there's a black wire though!



Yellow is just to trigger the starter relay and nothing else

Brown bypasses the ballast while cranking ( ign2 )
Blue is the circuit you are getting trouble ( ign1 ) which it uses to take very well to the ballast failure BUT:

The start up while cranking but stalling returning the key it can be anything from ballast, to bulkhead or ign switch. HOWEVER on this ocassion is not the ballast, because if you feed the coil from batt and engine keeps alive after crank it, the ECU is getting sourced from the same coil jumper wire THROUGHT the ballast ( assuming something of the rest is failing )

Go straight for the 12 volts check with key in RUN at ballast, or anywhere into the blue wire circuit... regulator, alt field, choke control feed or even the interlock reset button plug. This would take to the bulkhead connection at engine harness.

This failure will take to get off the brake light on cluster while cranking.

On normal conditions an underdash harness never needs really a full replacement unless previous owners got it highly "highjacked". The tipical failures on them is the Charging circuit network which when fails to the max, it takes to death the wires around them up to ammeter what due overheats caused by a heavy short it melts all around. The first diagnosis for them is a melted bulkhead conection caused by the low rate amps installed on our cars from factory giving over stressed the charging circuit, along with the low capacity of the packard terminals to hold the high stress on them, but if wire is still good, a deep mantenience on terminals and a bulkhead replacement is quite enough. Some of the fails with the bulkhead is not more than dirt and grease on terminals.

However it's weird you can't start up the engine with the new switch. You should get AT LEAST the same problem than with the original switch ( which I would try to keep on car )

Maybe I'm better off with the old switch as you recommend. I've turned a small problem into a bigger one by changing that switch already. Additionally- I will scrub and contact clean the bulkhead- it's pretty dirty on the engine side of the firewall. There were dirt dobber and wasp nests everywhere on this thing- I believe it sat for quite a while.

 

[WheelsOfTerror]

View attachment 962231 This is the replacement switch I meant. If you got one with this wire circled on plug, remove it. Some good brand replacements it use to get instructions sheets with them but most they don't

Remove the thin gauge black wire from the new switch ( it it got it ). Replacement switches use to have this provision for some later cars which needs to require it for some weird ground signal while cranking as far I recall, AND on our cars it matches with an orange wire for column shifter light. If you try to crank up some day the engine with lights on, will blow the cluster light fuse.

I didn't see this on my original reply- I did this and now that I read I realize I did the right thing. Glad to know the weird reason there's a black wire though!

 

[Nacho-RT74]

Well, if your car is a column shifter you had to remove it anyway To reinstall the orange coming from shifter light LOL. But those with floor shifter light doesn’t take care with that and could get the short, because the orange wire on dash harness is allways there no matter if floor or column shifter.

somebody posted the full instructions sheet for these ign switches and I saved it but dunno If I have it on my laptop or or my desktop. But my Desktop is in Venezuela while I’m in Spain LOL. I have a HDD with my last Desktop back up but I know it got a virus

The red wires coming from column which matches with black wires on dash harness are for the key in sensor for the warning buzzer. ( I know you didn’t ask, but just in case )

 

[WheelsOfTerror]

Well, if your car is a column shifter you had to remove it anyway To reinstall the orange coming from shifter light LOL. But those with floor shifter light doesn’t take care with that and could get the short, because the orange wire on dash harness is allways there no matter if floor or column shifter.

somebody posted the full instructions sheet for these ign switches and I saved it but dunno If I have it on my laptop or or my desktop. But my Desktop is in Venezuela while I’m in Spain LOL. I have a HDD with my last Desktop back up but I know it got a virus

The red wires coming from column which matches with black wires on dash harness are for the key in sensor for the warning buzzer. ( I know you didn’t ask, but just in case )

thanks dude- diving in shortly to see what I can find. I'll let you know!

 

[WheelsOfTerror]

Updates:
1. First thing first- prior to any of these troubles I fried the yellow wire running to the alternator- it disconnected from the alternator while I had it off the bracket to replace some mechanical things (timing chain, water pump, fan clutch, etc...) I tried to start it and got a smoke show. I replaced this wire nice and clean before seeking out this thread.

2. Today, encased in electrical tape behind the carb I found that the fried yellow wire had been twist-tied together with a bunch of other wires like this. You can see a bit of that wire that fried:

 

[WheelsOfTerror]

thanks dude- diving in shortly to see what I can find. I'll let you know!

3. So, dumbly, I wired it as I found it, planning to clean it up with a harness or some such solution later, but for the purposes of troubleshooting I wired it as I found it. This picture was after I cut them to make better connections and twisted them back together prior to me soldering all these wires and taping them up:

 

[WheelsOfTerror]

Well, if your car is a column shifter you had to remove it anyway To reinstall the orange coming from shifter light LOL. But those with floor shifter light doesn’t take care with that and could get the short, because the orange wire on dash harness is allways there no matter if floor or column shifter.

somebody posted the full instructions sheet for these ign switches and I saved it but dunno If I have it on my laptop or or my desktop. But my Desktop is in Venezuela while I’m in Spain LOL. I have a HDD with my last Desktop back up but I know it got a virus

The red wires coming from column which matches with black wires on dash harness are for the key in sensor for the warning buzzer. ( I know you didn’t ask, but just in case )

4. You might already be chuckling now, because the effect of this wire job was:
a. the car started up perfectly and ran and idled for about 20 seconds
b. the wires (and probably also the ballast at least) fried, smoked and burned up.

I didn't get a shot of the smoke, but they came from these two areas:

 

[WheelsOfTerror]

Well, if your car is a column shifter you had to remove it anyway To reinstall the orange coming from shifter light LOL. But those with floor shifter light doesn’t take care with that and could get the short, because the orange wire on dash harness is allways there no matter if floor or column shifter.

somebody posted the full instructions sheet for these ign switches and I saved it but dunno If I have it on my laptop or or my desktop. But my Desktop is in Venezuela while I’m in Spain LOL. I have a HDD with my last Desktop back up but I know it got a virus

The red wires coming from column which matches with black wires on dash harness are for the key in sensor for the warning buzzer. ( I know you didn’t ask, but just in case )

5. Lesson (re)learned:look at the wire diagram, don't just replace it and leave it how you (think you) found it.

Question- 1. which of these wires did the yellow one connect to that sent power to the coil, or am I hotwiring it in some dumb way it isn't supposed to be hotwired? (tests revealed power to coil was the start issue- resolved briefly when all the wires were twisted together)
2. Obviously I should pull the wires connecting the yellow to the ballast, since that was what blew up- but I know this thing ran prior to my experiments- I wonder why and how it EVER ran, and why it fried when I just tried my dumb experiment.

Isn't it fun to watch a guy that doesn't know what the hell he is doing figure it out the hard way?? cheers

 

[WheelsOfTerror]

5. Lesson (re)learned:look at the wire diagram, don't just replace it and leave it how you (think you) found it.

Question- 1. which of these wires did the yellow one connect to that sent power to the coil, or am I hotwiring it in some dumb way it isn't supposed to be hotwired? (tests revealed power to coil was the start issue- resolved briefly when all the wires were twisted together)
2. Obviously I should pull the wires connecting the yellow to the ballast, since that was what blew up- but I know this thing ran prior to my experiments- I wonder why and how it EVER ran, and why it fried when I just tried my dumb experiment.

Isn't it fun to watch a guy that doesn't know what the hell he is doing figure it out the hard way?? cheers

final update for today- I changed the ECU and the ballast and I'll wire it all up tomorrow after a good look at the wire diagram, hopefully with minimal explosions

 

[Nacho-RT74]

the black wire with eyelet terminal to the wiper motor mount stud got in short with some positive wire. That eyelet ground is /was to the reset interlock button

yellow wire to alt stud ? originally should be black 12 gauge. The only yellow wires on stock harness should be the ones to starter relay and interlock reset button. The wire to + lead of coil should be brown

maybe the black ground wire originally to reset button was linked to the black wire to alt stud ?... well thats a big short! But fuse link at starter relay should blown!

the deal is the harness was already hacket out and need to be rebuilt or replaced ( is available new if you care ).

I can make a colored diagram for you if you decide to fix/rebuilt. ( maybe I already have it!!! )

 

[Nacho-RT74]

I didn't have the 74 specifically but had another made for 73 and 72, so just had to modify one of them a bit.

Colors should be the correct ones

 

[WheelsOfTerror]

I didn't have the 74 specifically but had another made for 73 and 72, so just had to modify one of them a bit.

Colors should be the correct ones

View attachment 963539

man this is huge- I'm going to go down to the driveway and make this right now. I'll let you know how it goes. Thanks Nacho!

 

[Rusty 72]

Oh man that wiring job looks like a mess. I had the melted harness Nacho spoke of when I got my non running 72. I was able to source a used harness in good working order for the engine compartment for not too much money.
Might be the better route to take.
Good luck!

 

[WheelsOfTerror]

Oh man that wiring job looks like a mess. I had the melted harness Nacho spoke of when I got my non running 72. I was able to source a used harness in good working order for the engine compartment for not too much money.
Might be the better route to take.
Good luck!

thanks dude!

I actually have all the under hood and interior wiring off of a '72- when I got the smoke genie yesterday I was able to replace the ballast, and other odd parts cannibalizing that one. I actually went out there with Nacho's diagram and got it wired up and started, idling, not exploding, in like 20 minutes flat. Eureka!! Since it works, and I did clean wiring everywhere I touched, I am going to let it ride and try and avoid installing a new harness. Among other things I solder for a living so it's pretty clean work under there now.

Beyond the scope of this thread- the things left to do before it can drive are:

1. reassembling steering column
2. mounting the seats, mirrors, sun visors
3. change the oil filter (banged it up when I replaced the harmonic balancer)
4. fluids
5. tape up the electric wiring I just tore to pieces to fix, and also route the plug wires so I don't melt them on the headers
6. Install the third Wilwood brake proportioner (the first two leaked- one my fault one theirs) and bleed the brakes
7. replace valve cover gaskets (I did this already but one leaks pretty nasty so I get to do it again lol)
8. reclamp the fuel line in one spot- I saw a leak this morning.

It's a lot of little things but nothing as hard as chasing down the rat's nest wiring issue y'all just helped me find. Thanks Nacho, and thanks B Bodies only! This forum resource is completely indispensable.

Attached is a photo of it coming in on the car carrier last August. It's been a LONG road getting this thing to drive- and we are pretty much there!